2013-04-02 14:02:10 +00:00
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< h1 > precision_fortran.F< / h1 > precision_fortran.F How to control precision when coding a grib field.< p >
2015-01-05 15:45:46 +00:00
< div class = "fragment" > < pre class = "fragment" > < a name = "l00001" > < / a > 00001 C Copyright 2005-2015 ECMWF
2013-04-02 14:02:10 +00:00
< a name = "l00002" > < / a > 00002 C This software is licensed under the terms of the Apache Licence Version 2.0
< a name = "l00003" > < / a > 00003 C which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
< a name = "l00004" > < / a > 00004 C
< a name = "l00005" > < / a > 00005 C In applying this licence, ECMWF does not waive the privileges and immunities granted to it by
< a name = "l00006" > < / a > 00006 C virtue of its status as an intergovernmental organisation nor does it submit to any jurisdiction.
< a name = "l00007" > < / a > 00007 C
< a name = "l00008" > < / a > 00008 C
< a name = "l00009" > < / a > 00009 C Fortran 77 Implementation: precision
< a name = "l00010" > < / a > 00010 C
< a name = "l00011" > < / a > 00011 C Description: how to control < span class = "keyword" > decimal precision< / span > when packing fields.
< a name = "l00012" > < / a > 00012 C
< a name = "l00013" > < / a > 00013 C
< a name = "l00014" > < / a > 00014 C Author: Enrico Fucile
< a name = "l00015" > < / a > 00015 C
< a name = "l00016" > < / a > 00016 C
< a name = "l00017" > < / a > 00017 C
< a name = "l00018" > < / a > 00018 program precision
< a name = "l00019" > < / a > 00019 implicit none
< a name = "l00020" > < / a > 00020 integer maxNumberOfValues
< a name = "l00021" > < / a > 00021 parameter (maxNumberOfValues=10000)
< a name = "l00022" > < / a > 00022 include 'grib_api_f77.h'
< a name = "l00023" > < / a > 00023 integer*4 size
< a name = "l00024" > < / a > 00024 integer infile,outfile
< a name = "l00025" > < / a > 00025 integer igrib
< a name = "l00026" > < / a > 00026 real*8 values1(maxNumberOfValues)
< a name = "l00027" > < / a > 00027 real*8 values2(maxNumberOfValues)
< a name = "l00028" > < / a > 00028 real*8 maxa,a,maxv,minv,maxr,r
< a name = "l00029" > < / a > 00029 integer*4 decimalPrecision,bitsPerValue1,bitsPerValue2
< a name = "l00030" > < / a > 00030 integer i
< a name = "l00031" > < / a > 00031
< a name = "l00032" > < / a > 00032 call grib_check(grib_open_file(infile
< a name = "l00033" > < / a > 00033 X,'../../data/regular_latlon_surface.grib1','r'))
< a name = "l00034" > < / a > 00034
< a name = "l00035" > < / a > 00035 call grib_check(grib_open_file(outfile
< a name = "l00036" > < / a > 00036 X,'../../data/regular_latlon_surface_prec.grib1','w'))
< a name = "l00037" > < / a > 00037
< a name = "l00038" > < / a > 00038 C a new grib message is loaded from file
< a name = "l00039" > < / a > 00039 C igrib is the grib < span class = "keywordtype" > id< / span > to be used in subsequent calls
< a name = "l00040" > < / a > 00040 call grib_check(grib_new_from_file(infile,igrib))
< a name = "l00041" > < / a > 00041
< a name = "l00042" > < / a > 00042 C bitsPerValue before changing the packing parameters
< a name = "l00043" > < / a > 00043 call grib_check(grib_get_int(igrib,'bitsPerValue',bitsPerValue1))
< a name = "l00044" > < / a > 00044
< a name = "l00045" > < / a > 00045 C get the size of the values array
< a name = "l00046" > < / a > 00046 call grib_check(< a name = "a0" > < / a > < a class = "code" href = "group__get__set.html#g18b622ed86b24d5e5fcab70c309fc245" title = "Get the number of coded value from a key, if several keys of the same name are present..." > grib_get_size< / a > (igrib,"values",size))
< a name = "l00047" > < / a > 00047
< a name = "l00048" > < / a > 00048 C get data values before changing the packing parameters*/
< a name = "l00049" > < / a > 00049 call grib_check(grib_get_real8_array(igrib,"values",values1,size))
< a name = "l00050" > < / a > 00050
< a name = "l00051" > < / a > 00051 C setting decimal precision=2 means that 2 decimal digits
< a name = "l00052" > < / a > 00052 C are preserved when packing.
< a name = "l00053" > < / a > 00053 decimalPrecision=2
< a name = "l00054" > < / a > 00054 call grib_check(grib_set_int(igrib,"changeDecimalPrecision"
< a name = "l00055" > < / a > 00055 X,decimalPrecision))
< a name = "l00056" > < / a > 00056
< a name = "l00057" > < / a > 00057 C bitsPerValue after changing the packing parameters
< a name = "l00058" > < / a > 00058 call grib_check(grib_get_int(igrib,"bitsPerValue",bitsPerValue2))
< a name = "l00059" > < / a > 00059
< a name = "l00060" > < / a > 00060 C get data values after changing the packing parameters
< a name = "l00061" > < / a > 00061 call grib_check(grib_get_real8_array(igrib,"values",values2,size))
< a name = "l00062" > < / a > 00062
< a name = "l00063" > < / a > 00063 C computing error
< a name = "l00064" > < / a > 00064 maxa=0
< a name = "l00065" > < / a > 00065 maxr=0
< a name = "l00066" > < / a > 00066 maxv=values2(1)
< a name = "l00067" > < / a > 00067 minv=maxv
< a name = "l00068" > < / a > 00068 do i=1,size
< a name = "l00069" > < / a > 00069 a=abs(values2(i)-values1(i))
< a name = "l00070" > < / a > 00070 if ( values2(i) .gt. maxv ) maxv=values2(i)
< a name = "l00071" > < / a > 00071 if ( values2(i) .lt. maxv ) minv=values2(i)
< a name = "l00072" > < / a > 00072 if ( values2(i) .ne. 0 ) then
< a name = "l00073" > < / a > 00073 r=abs((values2(i)-values1(i))/values2(i))
< a name = "l00074" > < / a > 00074 endif
< a name = "l00075" > < / a > 00075 if ( a .gt. maxa ) maxa=a
< a name = "l00076" > < / a > 00076 if ( r .gt. maxr ) maxr=r
< a name = "l00077" > < / a > 00077 enddo
< a name = "l00078" > < / a > 00078 write(*,*) "max absolute error = ",maxa
< a name = "l00079" > < / a > 00079 write(*,*) "max relative error = ",maxr
< a name = "l00080" > < / a > 00080 write(*,*) "min value = ",minv
< a name = "l00081" > < / a > 00081 write(*,*) "max value = ",maxv
< a name = "l00082" > < / a > 00082
< a name = "l00083" > < / a > 00083 write(*,*) "old number of bits per value=",bitsPerValue1
< a name = "l00084" > < / a > 00084 write(*,*) "new number of bits per value=",bitsPerValue2
< a name = "l00085" > < / a > 00085
< a name = "l00086" > < / a > 00086 C write modified message to a file
< a name = "l00087" > < / a > 00087 call grib_check(grib_write(igrib,outfile))
< a name = "l00088" > < / a > 00088
< a name = "l00089" > < / a > 00089 call grib_check(grib_release(igrib))
< a name = "l00090" > < / a > 00090
< a name = "l00091" > < / a > 00091 call grib_check(grib_close_file(infile))
< a name = "l00092" > < / a > 00092
< a name = "l00093" > < / a > 00093 call grib_check(grib_close_file(outfile))
< a name = "l00094" > < / a > 00094
< a name = "l00095" > < / a > 00095 end
< a name = "l00096" > < / a > 00096
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